1. Field of the Invention
The present invention relates to a variable-frequency oscillator, and more particularly, to a variable-frequency oscillator that varies, even when a frequency of an input signal is varied, a frequency of an oscillation signal according to the varied frequency of the input signal.
2. Description of the Related Art
Recently, liquid crystal displays (LCDs) have been widely used in a variety of display devices, such as monitors and televisions, to provide small, lightweight, and thin LCD products.
LCD backlight units that turn on lamps of the LCD to output necessary light are inevitably used in the LCD products. The LCD backlight unit includes a driving IC for driving the lamps according to a predetermined frequency. The driving IC includes an oscillator that provides the frequency.
Video signals, such as a horizontal synchronization signal and a vertical synchronization signal, which are used in an LCD panel, are used in the LCD product. The interference occurring between the frequency of the voice signal and the frequency of the driving IC may cause a waterfall or a flicker on the LCD product. Thus, the frequency of the voice signal and the frequency of the driving IC need to be synchronized with each other.
FIG. 1 is a configuration view illustrating an oscillator according to the related art.
Referring to FIG. 1, an oscillator 10 according to the related art performs a logic operation L according to comparison results from first and second comparators C1 and C2 that compare charging and discharging voltages with predetermined first and second reference signals, respectively, to generate a charging and discharging switching signal. A first current source CS1 and a second current source CS2 charge and discharge a capacitor C according to opening and closing of a switch SW that performs a switching operation according to the charging and discharging switching signal, so that the oscillator 10 outputs first and second output signals.
The oscillator according to the related art outputs the first and second output signals each having a fixed frequency. When the frequency of a voice signal is varied, the frequency of each of the first and second output signals cannot be synchronized with that of the video signal. Therefore, a waterfall or a flicker may occur on the LCD product.